EspoCRM has authenticated SSRF via internal-host validation bypass using alternative IPv4 notation_CVE-2026-33534

{
    "lastseen": "",
    "description": "EspoCRM is an open source customer relationship management application. Versions 9.3.3 and below have an authenticated Server-Side Request Forgery (SSRF) vulnerability that allows bypassing the internal-host validation logic by using alternative IPv4 representations such as octal notation (e.g., 0177.0.0.1 instead of 127.0.0.1). This is caused by HostCheck::isNotInternalHost() function relying on PHP's filter_var(..., FILTER_VALIDATE_IP), which does not recognize alternative IP formats, causing the validation to fall through to a DNS lookup that returns no records and incorrectly treats the host as safe, however the cURL subsequently normalizes the address and connects to the loopback destination. Through the confirmed /api/v1/Attachment/fromImageUrl endpoint, an authenticated user can force the server to make requests to loopback-only services and store the fetched response as an attachment. This vulnerability is distinct from CVE-2023-46736 (which involved redirect-based SSRF) and may allow access to internal resources reachable from the application runtime. This issue has been fixed in version 9.3.4.",
    "published": "2026-04-13T19:20:04.414Z",
    "modified": "2026-04-13T19:20:04.414Z",
    "type": "cve",
    "title": "EspoCRM has authenticated SSRF via internal-host validation bypass using alternative IPv4 notation",
    "source": "GitHub_M",
    "references": "https://github.com/espocrm/espocrm/security/advisories/GHSA-h7gx-8gwv-7g73\nhttps://github.com/espocrm/espocrm/releases/tag/9.3.4",
    "id": "CVE-2026-33534",
    "bulletinFamily": "",
    "cwe": [
        "CWE-918"
    ],
    "cvelist": null,
    "sourceData": "espocrm espocrm < 9.3.4",
    "sourceHref": "",
    "cvss": {
        "score": 4.3,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "espocrm",
    "version": "< 9.3.4",
    "vendor": "espocrm",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}